Conventionally, in order to play back an image such as a movie, advertisement or the like in a theater, a two-dimensional image is projected on a single screen placed on the front side of the theater. However, the audience has no choice but to watch only the two-dimensional (2D) image in such a system.
Recently, techniques related to 3D images have been developed to provide images having a sense of depth to the audience, and the 3D image techniques use a principle of feeling a sense of depth even from a planar image if different images respectively enter left and right eyes of a person and merge together in the brain, in which two cameras having different polarized light filters are used when an image is taken, and a user wears glasses or the like having polarized light filters when watching the image so that different images may enter the left and right eyes.
However, although the 3D techniques may provide images having a sense of depth to users, there is a limit in that it is difficult to be absorbed in the image itself since it is merely watching an image played back on a single screen. In addition, there is also a limit in that the direction of the sense of depth felt by the audience is restricted to the direction where the single screen exists. In addition, since the conventional 3D techniques require the audience to wear glasses or the like having polarized light filters when watching an image, it is inconvenient for the audience who watch the image, and since different images are artificially and forcibly injected into the left and right eyes, sensitive audience may feel dizzy or nausea.
Accordingly, a so-called ‘multi-projection system’ which can solve the problems of the conventional projection system based on a single screen has been proposed, and the ‘multi-projection system’ mentioned here means a technique capable of providing a sense of depth and a sense of immersion to the audience by arranging a plurality of projection surfaces around the audience seats and playing back an image having a sense of unity on the plurality of projection surfaces. In addition, a ‘multi-projection theater’ means a theater in which the ‘multi-projection system’ is constructed. FIG. 1 shows an example of the multi-projection system.
In order to effectively operate the ‘multi-projection system’, a technique capable of effectively correcting images projected on a plurality projection surfaces is needed. It is since that in the ‘multi-projection system’, a plurality of images projected on a plurality of projection surfaces, not on a single projection surface, should be integratedly corrected, and the method of correcting a plurality of images should be changed as the structure of a theater changes, and, therefore, an image correction process is very complicated, and an error is highly probable to occur. Accordingly, techniques which can help the image correction process of the ‘multi-projection system’ are required.
Meanwhile, in addition to the multi-projection system, there are some cases in which images are projected on a single projection surface using a plurality of projectors. For example, there are some cases in which a projection surface is too wide or a horizon-to-vertical ratio of a projection surface is not covered by one projector.
When an image should be projected using a plurality of projectors, it is very important to provide an image having a sense of unity. Particularly, an image should be corrected so that boundaries of images projected by the projectors or overlapped and non-overlapped areas cannot be distinguished.